Denford stepper motor

[Edendale]

I have a denford microrouter that just been converted to Mach3, everthing seemed to work ok but 5 minutes into the first job it suddenly stopped and the y axis sounded like a machine gun, I tried to move the y axis with the keyboard it won’t move & just keeps making rattling sound, I reset the controller and it started to move ok until it stopped again and made the same rattling sound, could it be the stepper motor at fault or the ball nut, how would I find out which one is is causing the problem, also where could I find replacement parts, Thankyou. Mike